Effect of Cu Co-doping on the magnetism of Zn0.95Co0.05O films

Abstract

Zn0.95−xCo0.05CuxO (atomic ratio, x = 0–8%) thin films are fabricated on Si(111) substrate by reactive magnetron sputtering method. Detailed characterizations indicate that the doped Cu ions substitute the Zn2+ ions in ZnO lattice. The doped Cu ions are in +1 and +2 mixture valent state. The ferromagnetism of the Zn0.95−xCo0.05CuxO film increases gradually with the increase of the Cu+ ion concentration till x = 6%, but decreases for higher Cu concentration. Experimental results indicate that the increase of ferromagnetism is not owing to the magnetic contribution of Cu+ ions themselves, but owing to the enhancement of magnetic interaction between Co2+ ions, which suggests that p-type doping of Cu+ ions plays an important role in mediating the ferromagnetic coupling between Co ions.